This invention relates to a cargo handling system primarily, but not exclusively, intended for use in handling load units in the cargo compartment of an aircraft.
Conventionally a cargo compartment of an aircraft is provided with a plurality of roller tracks which provide a low friction support along which load units in the form of cargo containers or pallets can be transported along the length of the cargo compartment. It is known to drive the load units from an endless drive member in the form of a belt or chain extending parallel to the roller tracks. A carriage secured to the endless drive member is provided with an abutment element which engages a load unit during movement of the endless drive member and pushes the load unit along the roller track.
U.S. Pat. No. 4,154,334 discloses such an arrangement, and discloses also that the abutment member may be pivotally mounted on the carriage, and spring urged to a position in which it can abut a load unit. Stop means on the abutment member and the carriage limit pivoting movement of the abutment member relative to the carriage in one direction so that for movement in an appropriate direction the abutment cannot pivot further relative to the carriage and thus forms a fixed abutment engaging the load unit and transmitting drive thereto. However, as the carriage moves in the opposite direction the abutment can be pivoted against the spring bias, relative to the carriage, by engagement with a load unit, so that it passes beneath the load unit and does not transmit drive to the load unit. The abutment member and its associated stop means is reversible in position relative to the carriage, by manual adjustment, to reverse the direction of movement of the carriage in which the abutment transmits drive to a load unit. It will be recognised therefore that in the arrangement disclosed in U.S. Pat. No. 4,154,334 the abutment member normally occupies a position in which it will abut a load unit, and manual intervention is required in order to reverse the direction of travel of the carriage in which the abutment is effective to transmit drive to a load unit. It is an object of the present invention to provide a cargo handling system which avoids the difficulties of manual intervention in a simple and convenient manner.
In accordance with the present invention there is provided a cargo handling system comprising an elongate endless drive arrangement extending along the intended path of travel of a load unit in use, the endless drive arrangement including a carriage movable along said path and a load unit engaging member on the carriage and movable relative thereto between a load unit engagement position and an inoperative position in response to relative movement between first and second elements of the endless drive arrangement.
Preferably said endless drive arrangement includes an elongate drive belt or chain the opposite ends of which are coupled to said carriage so that the belt or chain and the carriage define a loop, said first and second elements of the drive arrangement being the opposite ends of said drive belt or chain respectively.
Conveniently the coupling of at least one of the ends of said belt or chain to the carriage permits movement of said end relative to the carriage to provide said relative movement between the first and second elements of the arrangement to actuate said load unit engaging member.
Conveniently the opposite ends of said drive belt or chain are moved relative to one another by increasing and decreasing the tension in the drive belt or chain.
Preferably the tension in the drive belt or chain is varied by an adjustable pulley arrangement co-operating with the drive chain or belt.
Alternatively said drive arrangement comprises first and second drive chains or belts coupled to said carriage, said first and second chains or belts defining the first and second elements of the drive arrangement respectively, and being movable relative to one another to actuate said load engaging member.